Key technology of gob-side entry retained by roof cutting without coal pillar for hard main roof: A typical case study

Abstract

This study results from the authors’ long-term efforts to develop key technology of gob-side entry retained by roof cutting under hard main roof. Three directions energy-gathered pre-splitting blasting device (TDEGPBD), open gob sealed technology with the flame retardant cement blanket (FRCB), and entry support with following mining states control ideology (FMSC) were proposed. The mechanical model of energy-gathered pre-splitting blasting with TDEGPBD was established. TDEGPBD can fracture rock mass in three directions and reduce roof suspension. Aiming at preventing spontaneous combustion of reserved coal in the gob, open gob sealed technology with FRCB was invented. It not only considers the space-time of gangue collapse but also realizes the goals of open gob rapid seal. Monitoring results show that CO, O₂, and CH₄ concentration decreased significantly to 0, 3.0257%, and 0.0899%, respectively. Following mining states control scheme considering the stages and the regions was proposed. The convergences of the roof near the cutting side and near the virgin coal side were 115 mm and 104 mm, respectively and the convergence between the gangue rib and virgin coal rib was 88.7 mm. These three key technologies provide an innovative approach and have significant application potential in non-coal pillar mining method.

Keywords

gob-side entry by roof cutting / three directions energy-gathered presplitting blasting device / flame retardant cement blanket / following mining states control ideology / effect analysis

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